A118496 Reverse digits of largest Chen primes, append to sequence if result is larger Chen prime then previous one with reverse digits.
2, 3, 5, 7, 11, 31, 71, 101, 701, 941, 971, 991, 9001, 9011, 9221, 9521, 9941, 70001, 76001, 97001, 99401, 99431, 99571, 99989, 940001, 973001, 987101, 993401, 997811, 999431
Offset: 1
Programs
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Maple
# Check if number is Chen prime ischenprime:=proc(n); if (isprime(n) = 'true') then if (isprime(n+2) = 'true' or numtheory[bigomega](n+2) = 2) then return 'true' else return 'false' fi fi end: #Reverse digits obrni_stev:=proc(n) local i, tren, tren1, st, ans; ans:=[ ]: tren:=n: tren1:=0: for i while (tren>0) do st:=round(10*frac(tren/10)): ans:=[op(ans), st]: tren:=trunc(tren/10): od: for i from 0 to nops(ans)-1 do tren1:= tren1 + op(nops(ans)-i, ans)*10^(i): od: return tren1 end: ts_inv_prav_chen_pra:= proc(n) local i, tren, ans; tren:=0: ans:=[ ]: for i from 1 to n do if (ischenprime(i)='true' and ischenprime(obrni_stev(i))='true' and obrni_stev(i)>tren) then ans:=[op(ans),obrni_stev(i)]: tren:=obrni_stev(i): fi: od: return ans end: ts_inv_prav_chen_pra(200000);
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